Regulating system



Dem 1935- A. s. FlTZ GERALD 2,925,534

REGULATING SYSTEM Original Filed Nov. 26, 1930 Inventor: Al an S. FitZGer'a l d,

His Attorney Patented Dec. 24, 1935' UNITED STATES PATENT OFFICEREGULATING SYSTEM I New York Continuation of application Serial No.498,416,

November 26, 1930.

This application March 26, 1932, Serial No. 601,388

Claims.

My invention relates to electrical regulating systems and moreparticularly to regulating systems employing electric discharge devicesor electric valves for controlling an electrical characteristic of adynamo-electric machine or circuit.

It is an object of my invention to provide a new and improved regulatingsystem employing electric discharge devices or electric valves forcontrolling an electrical characteristic of a dynamo-electric machine.

It is another object of my invention to provide a new and improvedregulating system that does not involve the use of moving contacts andis both sensitive and reliable in its operation.

A further object of my invention is to provide a new and improvedregulating system employing electric discharge devices which shallpossess the advantageous operating features of quick-actingelectro-mechanical regulators of the vibratory type without thedisadvantage of moving parts or contacts.

This application is a continuation of my copending joint applicationwith George W. Garman, Serial No. 498,416, filed November 26, 1930,entitled Regulating systems, and assigned to the assignee of the presentapplication.

The arrangement which is described in the prior joint application abovereferred to includes certain features, relating to a regulator and aregulating system of the Tirrill-type employing electric dischargedevices or electric valves, which are broadly claimed in thisapplication. These features include the alternate opening and closing ofthe electric valves for a variable number of successive cycles in amanner similar to the time-opened, time-closed effect of the vibratorycontacts of a Tirrill-type regulator, utilization of an electricalcharacteristic of the excitation circuit to prevent hunting, dampingmeans to prevent overshooting, and means to obtain proper regulatingaction in a polyphase cir cuit under conditions of single phase shortcircuits or faults.

The features of my invention which I believe to be novel and patentablewill be pointed out in the claims appended hereto. For a better-understanding of my invention reference is made to the followingdescription taken in connection with the accompanying drawing in whichthe single figure is a diagrammatic representation of one embodiment ofmy invention.

Referring to the single figure of the accompanying drawing, l denotes adynamo-electric machine shown as a synchronous three phase alternatorwhich is connected to a power circuit 2. The alternator l is providedwith a field winding 3 which is connected to be supplied with anexciting current from a source of direct current such as a directcurrent generator or exciter 4. The exciter 4 is provided with a fieldwinding 5 which is connected to be energized through electric dischargedevices or electric valves 6, I and 8 from the alternating currentterminals of the alternator or any other convenient alternating currentsource. These electric valves are each provided with an anode, acathode, and a control electrode or grid and are preferably of thegaseous or vapor electric type or any form of discontinuous control typeof valve because of the-greater current carrying capacity of this typeas now developed as compared to electric discharge devices or electricvalves of the pure electron discharge type in which the current flowingthrough the valve is continuously controlled by the potential upon thegrid. The term discontinuous control type of electric valve is intendedto mean that type in which the starting of current in the valve isdetermined by the potential of its control grid but in which the currentthrough the valve may be interrupted only by reducing the anodepotential below its critical value. Transforming means 9 are providedfor supplying current from the circuit 2 through the valves to the fieldwinding 5. This transforming means comprises a primary winding l0preferably delta connected and a secondary winding ll preferably zig-zagstar connected for eliminating direct current magnetization of thetransformer cores. The anodes of the valves 6, l, and 8 are connectedrespectively to different free terminals of the respective phasewindings of the secondary winding II. The neutral point of the starconnected secondary windings is connected to one side of the fieldwinding 5 and the other side of the field winding 5 is connected to thecathodes of the valves. The cathode of each valve is connected to aheating source through any suitable means and as illustrated atransformer I2 is connected across one phase of the alternator terminalsto energize the cathodes of each valve. An adjustable resistor I3 isconnected in series with the primary winding of transformer 12 foradjusting the value of the heating current. The

control electrode or grid of each valve is con-- of the valves 6, I, and8, respectively. A smbothing condenser |4'.is connected across'therecycle or predetermined number of cycles and block current during asucceeding cycle or predetermined number of cycles. As illustrated inthe drawing a unidirectional potential is obtained from the resistor Mwhich supplies a potential in one direction to make the valvesconducting and supplies a difierent potential in magnitude or polarityto prevent the current from starting through the valves.

In order to effect the control outlined above it is necessary to providemeans to vary the potential drop across the resistor It in accordancewith variations in the voltage or other electrical characteristic of themachine or circuit to be regulated. A change in voltage corresponding tothe change in the voltage to be regulated is produced by means of abalance or bridge circuit and a controlled rectifier. The balancecircuit performs the same function as the ordinary type of balancebridge circuit and comprises two transformers l8 and i9. Throughout theoperating range of the regulator, transformer 19 is arranged to saturatewith relatively low currents and transformer 18 is arranged to operatebelow saturation. The primary windings of these transformers areconnected in series and to the alternator terminals through a step-downtransformer 20. The secondary windings of these transformers are alsoconnected in series. It will be apparent that for one particular valueof current the voltage across the primary winding of each transformer isthe same and if these windings are connected in series and in the properphase relationship no voltage will exist across the terminals of thesecondary windings. However, if that particular value of current ischanged the circuit will be unbalanced and a difference voltage willexist. It will also be apparent that this difference voltage is afunction of the amount that the current is off balance, and that thephase relationship of the difference voltage depends upon whether thecurrent is above or below the balance value. In one case the differencevoltage will be approximately in phase with the line voltage and in theother case it will be approximately 180 degrees out of phase with theline voltage. Since the reactance of the transformers varies withfrequency it is necessary to utilize some means for preventing thebalance point from shifting for different frequencies. An adjustableresistance 2| is connected in series with the primary windings of thetransformers for reducing the frequency error and in addition it affordsan easy and simple means of changing the balance points so that theregulator will regulate for different line voltages. If the resistancein the circuit is in- .creased the current will decrease, therefore in,order to bring the current back to the balance value it is necessary tohold a higher line voltage. Obviously, the converse will reduce theregulatedline voltage.

"In the description of the balance circuit, immediately preceding, itwas stated that for a given balance current no voltage differenceexisted. That statement was not strictly accurate because a third orhigher harmonic is present in the. current wave, due to saturation inthe saturating transformer.- Therefore, in order to rechange, a low passfilter is used with a cutoif frequency of the order of 80 cycles. may beof any suitable type known in the art and by way of example I haveillustrated a typical network comprising two reactors 22 and 23connected in series with the circuit from the secondaries of the bridgetransformers and a condenser 26 connected to the junction between saidreactors and to the other side of the transformer secondary circuit. Inorder to keep the difference voltage from the bridge within safe limitsin case the generator voltage goes to a very high value due to suddenloss of load or any other reason, an impedance is connected in parallelto the series connected secondary windings of the balance circuit whichis arranged to have a high impedance for difference voltages below apredetermined value and a relatively low impedance for any difierencevoltage above the predetermined value. As illustrated, a transformer isemployed having its primary winding connected in shunt to the balancecircuit transformer and having its secondary winding connected to a glowtube 26. The glow tube might be connected directly across the balancecircuit transformer secondary'windings but it is more convenient to usea step-up transformer because of the range of difference voltage and theusual characteristics of the readily available glow tubes. The glow tubeis arranged to break down and pass current above a critical voltage andthereby prevent an abnormal voltage condition or phase modification ofthe voltage derived from 'the filter circuit.

Reviewing briefly, it will be noted that a circuit is provided in whicha difference voltage is obtained having a magnitude dependng upon theamount the line voltage is difierent from the value necessary to givethe balanced condition,

and having an in-phase or reversed-phase rela- 1 tion with respect tothe line voltage, depending upon whether the line voltage is above orbelow the balance point.

To increase the sensitivity of this circuit it is preferable to use ahigh ratio transformer 27 to step up this difference voltage. It hasbeen found that an amplification of one to twenty-five or one to fiftyis satisfactory. It must be clearly understood that the gain insensitivity is obtained not by increasing the magnitude of thedifference voltage but by increasing the change in the differencevoltage. That is, if there is a change of onevolt produced in thebalance circuit, and neglecting any loss in the low pass filter circuit,for

every volt change in the line voltage, either a This filter.

twenty-five volt or a fifty volt change will be produced in thesecondary winding of the transformer 27. The secondary winding of thistransformer is connected to two controlled rectifiers Z8 and 29preferably electric discharge devices of the high vacuum type. Theseelectric discharge devices are each provided with an anode, a cathodeanda control electrode or grid. The grids of the electric dischargedevices 28 and 29 are connected to be energized from the differencevoltage of the secondary winding of transformer 21 thereby controllingthe anode current of these tubes in accordance with variations in theline voltage. The impedance of the .grid circuit of the dischargedevices depends upon the grid voltage.

When it is negative the impedance is usualy very high, in the order ofmegohms, but if the grid is positive the impedance falls ofi veryrapidly and will perhaps be of the order of thousands of ohms.Therefore, if full sensitivity and amplification of the balance circuitand grid transformer is to be obtained it is necessary to work into ahigh impedance and the grid must, therefore, be negative. In order toincrease the sensitivity and amplification of this part of the circuitit has been found preferable to insert resistors 30 and 38, each of theorder of 400,000 ohms, in series with each grid. A condenser 32 isconnected between the grids for the purpose of reducing oscillations andlimiting the voltage across transformer 21.

The anode potential is obtained from the line voltage through atransformer 33 provided with a primary winding 34 and a secondarywinding 35 having opposite terminals connected to different anodes ofthe respective discharge devices. The primary winding 34 is connected tobe energized in accordance with the line voltage. An additionalsecondary winding 36 is provided for furnishing heating current to thecathodes of the discharge devices. This secondary winding is providedwith a midtap 39 which is connected by means of conductors 31 and 38 tothe midtap of the secondary winding of transformer 21 thereby completingthe cathode-grid circuit. Due to the amplification of the various partsof the circuit there is a large change in the anode current of thedischarge devices 28 and 29 with a small change in line voltage. Thischange in anode current manifests itself as a change in voltage across aresistance 40 connected in series relation with the anode circuit of thedischarge devices 28 and 29 by means of conductors 38 and 45. Thecircuit is so arranged that when the line voltage drops a small amountthere is a large increase in voltage across resistor 40.

In order to prevent the regulator from overshooting, it is desirable toprovide damping means performing the analogous function of the dashpoton the alternating current coil lever of a Tirrilltype of regulator. Thedamping is accomplished by charging a condenser 42 through a highresistance 43 by the voltage-appearing across resistance 40. The size ofthe condenser and the resistance through which the condenser is chargedis chosen of such a value that the time constant of this part of thecircuit is relatively long. To change the damping efiect it is thereforemerely necessary to change the value of the charging resistor.

7 If the regulator is used to regulate the voltage on a system in whichthe load is near or above the steady state limit it has been found thatthe voltage has a tendency to hunt soon after the steady state limit ispassed and that the voltage has a rising characteristic; the decreaseduring each oscillation being less than the increase. In order to avoidthis condition a resistance 44 is connected across the damping condenser42 so that the rising characteristic is reduced to a minimum within theoperating limits of the regulator.

The control circuit described so far gives 'a voltage across theresistor 44 which determines the voltage which is to be maintainedconstant. If this voltage were applied directly to the grids of thevalves 6, l, and 8 and caused these valves to pass current when the linevoltage was below a predetermined value and block current when the linevoltage was above a predetermined value it would not be entirelysatisfactory due to hunting. This hunting is inherent in the regulationof an alternator and is caused primarily by the self induction of thealternator field winding. Due to the self induction of the alternatorfield the alternator voltage with the simple control Just describedwould continue to increase for a time after the electric valves open andcontinue to decrease after the electric valves close resulting involtage oscillations having a high amplitude. It is, therefore,necessary to compare the change in alternator voltage with someelectrical quantity which is a definite and continuous function of theexcitation required by the alternator at normal voltage for any givenload condition. The voltage of exciter 4 is such a quantity and iscompared with the voltage appearing across the resistor 44 by means ofconductors 45 and 46. The time constant of the direct current circuit isrelatively small so that as the exciter voltage varies, the differencein the two voltages is impressed across a resistor M which in turn isused to control an amplifier circuit illustrated. as comprising twoelectric discharge devices 43 and 49 each having an anode, a cathode,and a grid. The grids are connected through grid resistors 50 and 58 toone side of the resistor 4i. The anode potential supply is obtained fromthe power circuit 2 and a convenient arrangement, as illustrated, is toconnect an anode transformer 52 across one phase of the transformer H0.The cathodes may be heated from any suitable source of current but inorder to make provision for proper regulation under conditions of ashort circuitor a fault on any one phase of a polyphase system thecathode heating current is obtained by means of transformer 53 from bothof the phases not connected to the voltage determining circuit. In caseof a short circuit on either of these two phases the emission of theelectric discharge devices will be reduced to a value which is too lowto control the electric valves 6, i, and 8 and the maximum amount ofexcitation will be supplied to the generator field.

Except for very low loads the circuit as outlined would have a tendencytohunt because of the high damping of the voltage determining circuit.In order to overcome this disadvantage and at the same time take care ofsudden changes in load, in particular above the steady state limit, acondenser 54 is placed across the resistance 43 in the damping circuit.This condenser has the function that for small changes in the balancevoltage the time constant is reduced sufiiciently to cause the excitervoltage to change immediately to the proper value. condenser isanalogous to a spring between the dashpot and plunger of the alternatingcurrent coil lever of the Tirrill type of regulator. By choosing theconstants of the damping circuit condenser 42 and resistance 53 and thequick response condenser 54 so that the time constant of the controlcircuit approaches that of the excitation circuit, oscillations in thealternator voltage due to the time delay in the excitation circuit maybe practically eliminated. The voltage circuit is thus capable ofcorrecting the voltage for small changes in the linevoltage'instantaneously but it cannot regulate during constantconditions. What actually occurs is that during constant load conditionsand power factor'the exciter part of the circuit functions in such amanner that the correct value of average field current is maintained inthe alternator field. In

case there is a sudden change in load the voltage circuit substantiallyinstantaneously causes the secondary control circuit to function andtends to restore the alternator voltage to normal.

Itis desirable to have the regulating range of the regulating systemfrom zero exciter armature voltage to the normal value for normal condi-The function of the tions. Zero exciter armature voltage is obtained bybucking down the normal residual exciter excitation by means of asub-exciter 55. The excitation due to the valves, 6, l, and 8, is inoppositionto that obtained from the sub-exciter so that for normaloperation the valve output will overpower the excitation due to thesub-exciter. However, for those conditions in which an exciter armaturevoltage is desired which is below the residual value, particularly forsynchronous condenser operation, the valve output is nearly cut ofi andthe sub-exciter overpowers the residual exciter field and residual valueoutput, thereby giving the desired value of exciter armature voltage.

In operation the average value of the output current of the valves 6, l,and 8 is varied. Suppose, for example, that the valves are allowed topass current for H] cycles and then are shut ofi for it cycles, thisaction being repeated indefinitely. It is quite obvious that if thebuild-up and build-down rates are the same, that the average value ofthe excitation will be 50% of the value that would be obtained if thevalves pass current continuously. Thus by varying the relative, durationof the time during which the valves are passing current to the timewhich they are shut off, the average value of excitation can becontrolled. This is exactly the method of operation of the regulatingsystem hereinbefore described.

To understand clearly the operation of this regulator and regulatingsystem, the action of an electro-mechanical regulator of the Tirrilltype, such as is described and claimed in United States Patent No.725,800, granted April '21, 1903 uponv an application of Allen A.Tirrill, should be clearly understood. The regulator disclosed in theaforementioned patent comprises a primary control element and asecondary control element. The function of the primary control elementis to determine under any given load condition and power factor, exactlywhat excitation is necessary to maintain the correct alternator voltage.The purpose of the secondary control element which is governed by thecontacts of the primary element, is to produce this excitation. Theprimary element consists of a multiple-spring biased lever actuated inresponse to exciter voltage and another damped and balanced leveractuated in response to the alternator voltage. The direct currentoperated lever carries the upper contact which cooperates with the lowercontact carried by the alternating cufientoperated lever. With theminimum exciter voltage the upper contact is at its extreme lowerposition and with maximum exciter voltage it moves upwards to the limitof its travel. The lower contact lever is balanced at the requiredalternator voltage and will move through its full travel with a smallvariation from normal alternator voltage.

Therefore, it is only necessary for the line voltageto change a verysmall amount to cause the lower contact to move a distance correspondingto the full range of travel of the upper con- .The secondary controlelement, which is called the relay, is arranged to short circuitsections aoeaaea of resistance in the exciter field circuitintermittently. The exciter armature voltage and therefore thealternator field current is varied by the relative duration of the timeduring which the relay contacts are closed or opened. For example, 5 asthe load on the alternator is increased, the period during which theresistance is short circuited is increased thereby maintaining a higheraverage value of exciter field current.

Assuming then that the regulator is holding it the correct voltage andthat the generator is not loaded, the contacts will be intermittentlyopening and closing. That is, as long as the load and power factorremain constant the excitation required by the alternator will remainconstant, 15 and due to the inductance of the alternator field any smallchanges occurring in the exciter voltage will not be reflected in thealternator voltage, but even if there is an instantaneous variation inalternator voltage no motion will be transmitted to the alternatingvoltage lever because it is damped. Therefore, the alternating voltagelever will remain fixed but as soon as the upper and lower contactsclose the exciter voltage will be increased thereby causing the upperlever to rise. This will immediately cause the relay contacts to openand insert resistance in the exciter field circuit which will cause theexciter voltage to decrease. This action will be repeated indefinitelyand thus by intermittently increasing and decreasing the exciterarmature voltage the correct average value of field excitation ismaintained.

If the load on the alternator is increased, the decreased output voltagewill permit the alternating voltage lever at the contact end to rise andthereby increase the exciter voltage. The alternating voltage lever willstay at this new position and the exciter voltage will vary about a newpoint which is higher than the previous do one and thereby require ahigher average exciter voltage to open the contacts. Conversely, if theload is decreased the contact end of the alternating voltage lever fallsand the exciter voltage will vary about a new and lower point therebyrequiring a lower average exciter voltage to open the contacts.

The operation of the embodiment of my invention illustrated in thesingle figure of the accompanying drawing will now be readilyunderstood.

'It will be assumed that the alternator is being driven by a suitableprime mover (not shown) and that the exciter residual voltage issufiicient to effect building up of the alternator voltage. At a voltagebelow the voltage to be maintained, or the balance voltage of thebridge, the difference voltage is arranged to be of such magnitude andphase relation as to increase the grid potential of the dischargedevices 28 and 29 in a positive direction so that the anode current ofthese discharge devices is increased and a unidirectional voltage isobtained across the resistor 66 which varies inversely with thealternator voltage. The voltage across the resistor ti) and consequentlythe voltage across resistor M under the low voltage condition isarranged to be greater than the exciter voltage which is in seriesopposition therewith. The polarity and magnitude of this resultantvoltage is such as to bias the grids of the amplifier discharge devicesQ8 and 49 in a 70 negative direction so as to make the anode current andconsequently the voltage drop across the control resistor It a minimum.Under this condition the valves 6,], and 8 are arranged to be r full-on.As a result the field excitation is increased and the exciter voltage isincreased to that value required for normal voltage. Just as soon as theexciter voltage attains the normal value the resultant voltage appliedto the grids of the amplifier discharge devices decreases the negativebias or increases the grid potential in a positive direction so that theanode current of these devices increases. As a consequence the voltagedrop across the resistor l4 increases in a negative direction to shutthe valves oil.

When the valves shut off the exciter voltage starts to decrease and theamplifier grid potential changes so as to put the valves full on again.The result is that the exciter field current is interruptedintermittently by the grid control action of the valves just as theresistor is open circuited intermittently in the electro-magnetic typeof regulator. The voltage across the resistor 44 remains practicallyconstant for a given load condition and corresponds to the relativelyfixed position of the contact carried by the alternating voltage leverof the Tirrill type of regulator, whereas the voltage component from theexciter rises and falls about a mean value similar to the vibrationabout a mean position of the contact carried by the direct current leverof the Tirrill type of regulator. This action causes the valves to shutoff and on to maintain an average alternator excitation corresponding tothe given load condition.

If the load on the alternator increases and the line voltage decreasesfrom the value to be maintained there is a large change in the voltageacross resistor 44, which corresponds to the large movement of the lowercontact of the Tirrill type of regulator for a small change in voltage.This action means that the exciter voltage does not have to vary as farfrom the mean value before the valves are full on so that the valves areon for a greater period of time than they are on. In other words, theratio of time-closed to timeopened of the valves is increased and themean average excitation of the alternator is increased to maintain thealternator voltage for the new load condition. For a decrease of loadand an increase in terminal voltage above the normal value the excitervoltage must vary farther from the mean value before the valves are fullon so that the valves are off for a greater period than they are on. Inother words, the ratio of timeclosed to time-opened of the valves isdecreased and the mean average excitation of the alternator is decreasedto maintain the alternator voltage for the new loadcondition.

While I have shown and described a particular embodiment of my inventionit will be obvious to those skilled in the art that changes andmodifications may be made without departing from my invention and I,therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a regulating system, an alternating current circuit, a directcurrent circuit for controlling an electrical characteristic of saidalternating current circuit, an electric valve connected tosaid directcurrent circuit for controlling the energi'zation thereof, and meansoperative in accorclance with, variations in the resultant voltagebetween a unidirectional voltage component of an electricalcharacteristic of said alternating current circuit and a unidirectionalvoltage component varying in accordance with an electricalcharacteristic of said direct current circuit for controlling saidvalve.

2. In a regulating system, an alternating current circuit, a directcurrent circuit for controlling an electrical characteristic of saidalter- 5 nating current circuit, a source of current for energizing saiddirect current circuit, an electric valve connected in series relationwith said direct current circuit and said source for controlling theenergization of said direct current circuit, and 10 means operative inaccordance with the difference between a unidirectional voltagecomponent varying in accordance with an electrical characteristic ofsaid alternating current circuit and a unidirectional voltage componentvarying in accord- 5 ance with an electrical characteristic of saiddirect current circuit for controlling said valve.

3. In a regulating system, a dynamo-electric machine having an armaturecircuit and an excitation circuit, an electric valve for contro ling 20the energization of said excitation circuit to control an electricalcharacteristic of said armature circuit, means for supplying aunidirectional voltage component varying in accordance with thedeviation from a predetermined normal value 25 of the electricalcharacteristic of said armature circuit, means for introducing in seriesopposition with the voltage component from said first mentioned means aunidirectional voltage component varying in accordance with anelectrical characteristic of said excitation circuit, and meansoperative in accordance with the resultant voltage of said voltagecomponents for controlling said valve.

4. In a regulating system, an alternating current circuit, a directcurrent circuit for controlling an electrical characteristic of saidalternating current circuit, an electric valve for controlling theenergization of said direct current circuit, and means operative inaccordance with an electrical characteristic of said direct currentcircuit for intermittently closing and opening said valve,

and means operative in accordance with an electrical characteristic ofsaid alternating current circuit for varying the ratio of time-closed totime-opened of said valve.

5. In a regulating system, a dynamo-electric machine having an armaturecircuit and an excitation circuit, an electric valve for controlling theenergization of said excitation circuit to control an electricalcharacteristic of said armature circuit, and means jointly responsive tothe voltage of said excitation circuit and the voltage of said armaturecircuit for closing and opening said valve during complete half cyclesof the alternating current circuit for successive periods of varyingduration.

6. In combination, an alternating current machine comprising excitationand armature circuits, a voltage determining circuit connected 50 tosaid armature circuit and arranged to furnish a difierence voltagevarying in accordance with the variation of an electrical characteristicof said armature circuit above or below a predetermined value, means forfurnishing a unidirectional voltage variable in magnitude in accordancewith said difierence voltage, means for combining said unidirectionalvoltage and a voltage component varying in accordance with anelectricalcharacteristic of said excitation circuit, an amplifier comprising 'anelectric discharge device provided with an anode circuit and a controlgrid, said control grid being connected to be energized in'-."accordance with the resultant voltage of said 7. The combinationwith a controlled circuitand a controlling circuit of means comprisingan electric valve having a control electrode, for controlling theenergization of said controlling circuit, means connected to saidcontrolled circuit for producing a component of voltage varying inaccordance with variations in an electrical characteristic of saidcontrolled circuit, an electric discharge device having a grid connectedto be energized in accordance with said component of voltage forcontrolling the potential of the control electrode of said valve, and adamping circuit comprising a condenser connected to be charged through aresistor from said component of voltage for delaying a change in thegrid potential of said discharge device.

' 8. The combination of a dynamo-electric machine comprising excitationand armature cirv cuits, means comprising an electric valve having acontrol electrode, for controlling the energization of said excitationcircuit, means for providing a source of voltage varying in accordancewith an electrical characteristic of said armature circuit, an electricdischarge device having a grid connected to have the potential thereofvaried in accordance with variations in said source of voltage, and adamping circuit interposed between said means and said grid and acondenser connected in series relation with a resistor with respect tosaid source of voltage for delaying a change in the grid potential ofsaid discharge device.

9. In combination, a polyphase alternating current circuit, an electricvalve for controlling an electrical characteristic of said circuit, andmeans connected to be energized from difierent phases of said circuitand operative in accordance with an unbalance of said electricalcharacteristic in different phases of said circuit for controlling saidvalve.

10. The combination of a polyphase alternating current machinecomprising excitation and armature circuits, means comprising anelectric valve having a control electrode, for controlling theenergization of said excitation circuit, a voltage determining circuitconnected to one phase of said machine and comprising an electricdischarge device for controlling said control electrode, and meansoperative in accordance with an unbalanced electrical condition of saidmachine below a predetermined value on any phase of said machine forrendering said valve fully conducting independently of said voltagedetermining circuit.

11. The combination of a polyphase alternating current machinecomprising excitation and armature circuits, means comprising anelectric valve having a control electrode, for controlling theenergization of said excitation circuit, a voltage determining circuitconnected to one phase of said alternating current machine comprising anelectric discharge device having a cathode, for

- controlling said control electrode, said cathode being connected todifferent phases than said cult, means comprising an electric valve forcontrolling an electrical characteristic of said regulated circuit,means for intermittently rendering said valve completely conductive andcompletely non-conductive, and means for varying the in- 5 tervals oftime during which said valve is completely conductive and completelynon-conductive.

13. In a regulating system, a regulated circuit, a control circuit forcontrolling an electrical 10 characteristic of said regulated circuit,means comprising electric valve means for controlling the energizationof said control circuit, means for alternately rendering said valvemeans continuously conductive for increasing said energization l5 andcontinuously non-conductive for decreasing said energization, and meansfor modifying said last-mentioned means for varying the intervals oftime during which said valve means is conductive and non-conductive.

14. In a regulating system, a regulated circuit, a control circuit forcontrolling an electrical characteristic of said regulated circuit,means v comprising electric valve means for alternately varying theenergization of said control circuit 25 between relatively high and lowvalues, means for rendering said valve means completely and continuouslyconductive during an interval of time sufificient for the attainment ofsaid high value of excitation and for rendering said valve 30 meanscompletely and continuously non-conductive during an interval of timesufiicient for the attainment of said low value of excitation, and meansfor varying the intervals of time during which said valve means isconductive and non- 3 conductive.

15. In a regulating system, a dynamo-electric machine having an armaturecircuit and an excitation circuit, means comprising electric valve meansfor controlling the energization ofsaid exto citation circuit, means forintermittently rendering said valve means completely conductive andcompletely non-conductive for abruptly increasing the energization ofsaidjexcitation circuit continuously during the period of conduc- 45tivity and abruptly decreasing the energization of said excitationcircuit continuously during the period of non-conductivity, and meansfor moditying said last-mentioned means for varying the intervals oftime during which said valve means 53 is completely conductive andcompletely nonconductive.

16. In a regulating system, a dynamo-electric machine having an armaturecircuit and an excitation circuit, means comprising electric valve5means for alternately varying the energization of said excitationcircuit betweenrelatively high and low values, said valve means beingprovided with a control electrode circuit, means for alternatelyapplying difierent potentials to said con- 6( trol electrode circuit forrendering said valve ineans completely and continuously conductiveduring an interval of time sumcient for the attainment of said highvalue of excitation and completely and continuously non-conductive dur-65 ing an interval of time sufiicient for the attainment of said lowvalue of excitation, and means for modifying said control electrodepotential for changing the intervals of time during which said valvemeans is conductive and non-conductive. Ti 17. In a regulating system,an electric circuit to be controlled, a controlling circuit in operativerelation with said electric circuit, means com-' prising an electricvalve having a grid circuit, for

controlling an electrical characteristic of said 7:

controlling circuit, means connected in circuit with said grid circuitfor intermittently closing and opening said valve, and means arranged tomodify the potential of said grid circuit and operative in accordancewith the voltage of said electric circuit for varying the ratio oftime-closed to time-opened of said valve.

18. In a regulating system, a dynamo-electric machine having an armaturecircuit and an excitation circuit, an electric valve for controlling theenergization of said excitation circuit to control an electricalcharacteristic of said armature circuit, means for intermittentlyclosing and opening said valve, and means responsive to an electricalcharacteristic of said armature circuit for varying the ratio oftime-closed to timeopened of said valve.

19. In a regulating system, an alternating current circuit, a directcurrent circuit for controlling an electrical characteristic of saidalternating current circuit, means comprising electric valve means forcontrolling the energization of said direct current circuit, means forrendering said valve means alternately conductive and nonconductiveduring complete half cycles of alternating voltage, and means operativein accordance with variations in an electrical characteristic of saiddirect current circuit for modifying the intervals of time during whichsaid valve means is conductive and non-conductive.

20. In a regulating system, a dynamo-electric machine having an armaturecircuit and an excitation winding, electric valve means for controllingthe energization of said excitation winding to control an electricalcharacteristic of said armature circuit, means for rendering said valvealternately conductive and non-conductive during complete half cycles ofalternating voltage, and means operative in accordance with changes ofcurrent in said excitation winding for changing the intervals of timesaid valve means becomes non-conducting and conducting.

21. In a regulating system, a regulated circuit, means comprising anelectric valve having a controlling circuit, for controlling anelectrical characteristic of said regulated circuit, means in operativerelation with said controlling circuit for intermittently closing andopening said valve, and means arranged to modify said second-mentionedmeans and operative in accordance with an electrical characteristic ofsaid regulated circuit for varying the ratio of time-closed totimeopened of said valve.

22. In apparatus of the character described, in combination, :a sourceof alternating current; and means for regulating a function of theoutput of said source, said means including an electronic conductiondevice having a control electrode, a winding energized by alternatingcurrent, a winding connected to be responsive to a function of theoutput of said source, core means related to said windings, one of saidwindings and said core means having a different saturationcharacteristic from said other winding and said core means, and meanscontrolled by the inductive effects produced by said windings foraffecting said control element.

23. In apparatus of the character described, in combination, a source ofalternating current; and means for regulating a function of the outputof said source, said means including an electronic conduction devicehaving a control electrode, a winding energized by alternating current,a winding connected to be responsive to a function of the output of saidsource, core means related to said windings, one of said windings andsaid core means having a different saturation characteristic from saidother winding and said core means, a secondary winding inductivelyrelated to said first-mentioned winding, a secondary winding inductivelyrelated to said secondmentioned winding, and means connecting saidcontrol element to be responsive to the difference between thepotentials induced in said secondary windings.

24. In apparatus of the character described, in combination, a source ofalternating current; and means for regulating a function of the outputof said source, said means including an electronic conduction devicehaving a control electrode, a winding energized by alternating current,a winding connected to be responsive to a'function of the output of saidsource, core means related to said winding, one of said windings andsaid core means having a different saturation characteristic from saidother winding and said core means,

a secondary winding inductively related to said first-mentioned winding,a secondary winding inductively related to said second-mentionedwinding, and a step-up transformer of relatively high ratio having itslow tension winding connected to be responsive to the difference in thevoltages of said secondary windings and having its high tension windingconnected to affect said control element.

25. The combination with a dynamo-electric machine having a fieldwinding, means for supplying an energizing current to said winding,means, comprising an electronic tube having a control-grid element, forcontrolling said enerr, gizing current, and a circuit for impressingupon said grid element a control potential determined by an electriccharacteristic of the said machine, of means for introducing into saidgrid circuit a compensating potential that varies in accordance with thecurrent in the field winding of said machine.

26. The combination with a dynamo-electric machine having a fieldwinding, an exciter for energizing said field winding, means, comprisingan electronic tube having a control-grid element for adjusting thevoltage of said exciter, and a circuit for impressing upon said gridelement a control potential determined by an electric characteristic ofthe said machine, of means for in- 5 troducing into said grid circuit amodifying potential that varies in accordance with the voltage impressedupon said machine-field winding.

27. The combination with a dynamo-electric machine having a fieldwinding, an exciter for 57, energizing said winding, means, comprisingan electronic tube having a control-grid element, for adjusting thevoltage of said exciter, and a circuit for impressing upon said gridelement a control potential determined by a characteristic of 0 the saidmachine, of means for introducing into said grid circuit a modifyingpotential that varies in accordance with the current energizing saidmachine-field winding.

28. In combination with an electrical generator having a field winding,means for supplying an exciting current to said winding, and aregulator, for controlling the voltage of said generator, comprisingelectronic-tube means having a grid element for controlling saidfield-winding current, and a circuit for impressing upon said gridelement a control potential determined by the voltage of the generator,means for introducing into said grid circuit a load-compensating controlpotentialthat varies in accordance with the said field-winding current.

29. In combination with a regulator for an electrical generator, saidregulator having an electron tube disposed in a circuit for controllingthe excitation of the generator in accordance with a potential impressedupon a grid element of said tube by a control circuit influenced by thegenerator voltage, generator-load-compensating means for said regulatorcomprising a resistor connected in said grid-element control circuit,said resistor being disposed to be acted upon by a current determined bythe excitation of the generator.

30. In combination with a regulator for an electrical generator having afield winding and an exciter for energizing said winding, said regulatorhaving an electron tube disposed in a circuit for controlling thevoltage of said exciter in accordance with a potential impressed upon agrid element of said tube by a circuit influenced by the generatorvoltage, generator-load compensating means for said regulator comprisinga resistor connected in said grid-element control 10 circuit, and meansfor causing to flow through said resistor a current determined by thevoltage of said exciter.

ALAN S. FITZ GERALD.

